Magnetic chuck.



R. G. PATTON. MAGNETIC CHUCK.

APPLICATION FILED 11211.25. 1912.

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MAGNETIC CHUCK. APPLICATION runnlrmza, 191g.

Patented Dec. 16, 1913.

' z alums-sum 2Q RALPH C. PAT'ION, F PROVIDENCE, RHODE COMPANY, OF PROVIDENCE, RHODE ISLAND,

ISLAND, ASSIGNOR TO D & W FUSE A CORPORATION OF RHODE ISLAND.

MAGNETIC CHUCK.

Specificationof Letters Patent.

Patent-ed'Dec. 16, 1913.-

Application filed April 25, 1912. Serial No. 693,252.

To all whom it may concern:

Be it known that I, RALPH C. PATTON, of Providence, Rhode Island, have invented new and useful Improvements in Magnetic Chucks, which invention in the following specification.

This invention relates to improvements in magnetic chucks, a class of devices designed for holding articles of magnetic material while undergoing machining operations, and has for its object to provide a device of the kind referred to which possesses a marked increased holding power for a given expenditure of energy; which prevents drag or movement of the piece of work either lengthwise or across the surface while undergoing machining operations and which quickly made without special tools. This has a low magnetic leakage.

A further object of the invention is to provide a water-tight joint peculiarly adapted for use ina magnetic-chuck'casing and which is simple, efiicient and can be improvement as herein described, but not claimed,forms the subject-matter of my copending application Serial No.-708,878, filed J uly'11, 19l2, wherein the same is claimed.

It has heretofore been proposed to con struct magnetic chucks with a single core and to provide the same with a plurality of oblong polar projections the ends of which lie in the face of the chuck with their longeraxes parallel to one edged the rectangular chuck casing. The directions in which machining movements usually occur with these forms of chuck are normal to the edges of the chuck face. When the movement is normal to the edge of the chuck and perpendicular to the elongated axes of the pole faces the sidewise drag onthe work is resisted whereas when the machining movement is parallel to the edge of the chuck and with the long axes of the pole faces, then there is less resistance to the drag on the Work. This difference in holding ower of the chuck in the two directions 0 movement of the machining operations detracts from the usefulness of chucks of this class, particularly when holding small pieces. Myinvention overcomes this objection by providing the core of the energizing magnet with one 'or more pole extensions or pieces set at an angle other than 90 to one edge of the rec tangular chuck face and also at an angle other than 90 to the longer dimension of is fully set forth .struction resides in groove 1n the edge these two working directions. These two directions are the' only directions in com mon practice in which there would be occasion to operate the to ols over the chuck face. Other important advantages flow from this construction such as increased holding power for a given expenditure of energy, the reduction of magnetic leakage and other advantages as will appear in the detailed description.

In using magnetic chucks, it is frequently necessary to flood the chuck'with water particularly during the process of grinding. Difliculty has arisen in making a water-tight joint between the casing walls and the -bottom plate of the chuck without interposing resistance to the flow of magnetic lines at that point such as results by the use of a gasket which necessitates a magnetic gap at i the joint. I have devised a calking joint which does not interfereto any appreciable extent with the flow of magneticliiies across the joint while securing the necessary degree of tightness to exclude water. While the details of construction of my calking joint maybe varied the essential feature of conproviding a reentering of the wall where the oint occurs adapted to receive and retaincalkin material such as hemp, twine or the like ich is rendered impervious to water by waterproofing material such as paint, pitch, shellac, varnish or similar materials. Either member of the joint may be provided with the retaining groove or both members may be so provided. The shape of the groove may take on various forms either curvilinear or angular provided that a reentering space is formed capable of acting to retain packing. This joint avoids the use i of gaskets while securing a water-tight joint and has the advantage of interfering with the flow of magnetic lines across the junction of the parts to a minimum degree.

In order that the invention may be clearly understood and readily carried into effect, I will describe the same with reference to so' I the constructional form embodying the invention represented by way of example in the accompanying drawings, in WhiCl1i Figure 1 is a perspective v ew of a magnetic chuck embodying my improvements. Fig. 2 is a plan view partly in section showing the angular arrangement of the pole faces and the interior construction. Fig. 3, is a erspective view of the magnet core with its pole projections. Fig. 4 is a vertical longitudinal section on the line 14 of F ig. 2. Fig. 5 is an enlarged detail showing my improved packing joint.

Referring to the drawings, the magnetic chuck comprises a base plate 1 having means such as slotted projections 2 for securing it to the bed plate of a planing or like machine; a magnet core 3 having elongated pole projections 4 which are arranged at an angle other than 90 to the longer axis of the core and are preferably integral therewith; a casing 5 adapted to be secured to the base plate and provided in its top face with elongated openings for receiving the ends of the pole projections which' are separated from the casing by gaps 10 filled with non-magnetic material and an energiz ing coil 6 which is preferably of the type which is wound with Deltabeston wire and can be readily replaced in case of accident to the coil. The core 3 may be secured to the plate 1 by any suitable securing means, such as by dowel pins 7 and screws 8. The casing, as illustrated, is secured to the base plate by corner bolts 9. The pole projections 4; are arranged and designed.

with a view of securing a plurality of polar areas 10 in the holding face of the chuck while securing a large cross-section for each projection whereby the magnetic reluctance through the projections may be minimized and further with a view of reducing the length of the path through the core and thereby reducing resistance to the magnetic lines. These results are accomplished in large measures by providing the core with projections which are elongated transversely of the long axis of the core instead of parallel with this axis as has heretofore been proposed. The neck 11 of each projection can thus be made as thick or even thicker than the thickness of the core while enabling many more projections to be formed on a single core than in the parallel arrangement referred to. The reluctance to the flow of the magnetic lines through that part of the magnetic circuit including the pole extensions is thereby materially reduced with a corresponding increase in the holding power of the chuck. Again this construction which permits increased spacing of the pole projections 4, 4, and also deepening of the spaces between these projections enables the portions 12 of the cover which are located between the pole projections 4, 4, and constitute parts of the magnetic circuit to be materially enlarged in cross-section without reducing the cross-section of the necks 11 of the pole rojections 4:, thereby further reducing the re uctance of the circuit while securing the advantages of short divided aths for the lines to flow between the po e areas 10 and the sides of the chuck through portions 1?. This is made plain by reference to F1g. 1. The magnetic lines which may beassumed to How from pole areas 10 pass nto sections 12 and therein find two paths indicated by the arrows 12 through which to return to the casing. This my arrangement of the pole projections enables reduction 1n the resistance to the flux and also shortens the path. Again theheight of the chuck has been enabled to be shortened about 17% by the fact of deepening the spaces between the pole extensions whereby the energizing coil may be raised on the necks of the projections with a gain in the reduction of leakage across the s'a'ce between the core and body of the chuck at 89, a gain in the reduction of material in the construction and a marked gain in holding power (if the. chuck Magnetic chucks designed to be clampe or held fast to a bed plate are almost 1111 versally' used in operations of grind ng or planing either lengthwise or crosswise of their faces. In order to resist the dra on the work during these operations I are discovered that the polar projections should also be angularlydlsposed t0 the edges of the chuck case. By reason of thlsangular disposition of the pole faces with the edges of the chuck in holdin small pieces th lines of force which ho d the work to the chuck must be disrupted before any effort to move the piece laterally or longitudinally can result in dragging the work under the action of the tools. The holding properties of the face are thus extended in two directions, lengthwise and across the face instead of in one direction as in the andlel arrangement above refererd to. hile the elongated pole projections 4 may be given any desired angular relation with the long axis of the core and the edge of the chuck between 0 and 90, Ihave found that in a chuck with five pole projections an angle of about 30 with the normal to the long axis of the chuck or core gives good results. I, however, give this merely as an example and do not desire to be limited to such specific angular relation. Another feature of my invention resides 1n an lmproved calking joint-particularly adapted for rendering the j i t f a netic .chuck water-tight. Fig 5 i an larged detail view showing the joint i SS-SeCt10n 1n which 13 is the wall of the casing provided on its outer edge with a dove-tail groove 14 which follows around the bottom of the casing. The third side of the packing joint is formed by the surface of the base plate 1. Into this holding space is packed calking material such as twine or the like saturated with waterproofing material such as shellac or some air drying varnish. It will be noted that this calking joint occupies but a small portion of the junction between the two magnetic surfaces across which the magnetic flux flows and therefore interferes but little with the magnetic circuit at this point while securing all the requisites of a water-tight joint without the use of a gasket which seriously interferes with the flux across the junction and with the holding power of the chuck. The packing can be readily removed for the purpose of gaining access to the interior of the casing and can be easily replaced without the use of any special tools.

In Figs. 1 and 2, I have shown a reversing switch attached to the chuck and have indicated the resistance coil 23 as inside the switch box for the sake of compactness though the switch and coil may be associated separately. The face of the chuck is shown provided with work holding pins 38 though side rests, of any well known type may be substituted as they form no part of the present invention.

\Vhat is claimed is 1. In a magnetic chuck, the combination of a magnetizing coil and a core for the same, one end of which is provided with a plurality of pole projections the faces of which are arranged parallel with each other and transversely of andat acute angles with the longest dimension of said core.

2. In a magnetic chuck, the combination of a magnetizing coil and a core for the same, one end of which is provided with a plurality of pole projections the faces of -Which are elongated and arranged parallel with each other and transversely of and at acute angles with the longest dlmension of said core.

3. In a magnetic chuck, the combination of a magnetizing coil, a core for the same, one end of which is provided with a plurality of pole projections the faces of which are arranged transversely of and at acute angles with the longest dimension of said core and a casing having one wall provided with openings for receiving the ends of said projections.

i. In a magnetic chuck, the combination of a magnetizing coil, a core for the same, one end of which is provided with a p111- -rality of pole projections the faces of which are arranged transversely of and at acute angles with the longest dimension of saidcore, and a rectangular casing having one face provided with openings for receiv ing'the ends of said projections, the longitudinal axis of the chuck making acute angles with said elongated projections.

5. A magnetic chuck having a rectangular holding face comprising a plurality of elongated areas of one polarity surrounde by an area of opposite polarity, the elongated areas being arranged parallel with each other and making acute angles with the edges of said holding face.

In testimony whereof I have signed this specification in the presence of two subscribing witnesses.

RALPH C. PATTON. 

